1. Field of the Invention
The present invention relates to zinc containing anticalculus dentifrice compositions. Specifically, the invention is directed to low pH dentifrice compositions employing one or more slightly soluble zinc compounds as the active agent. Even more specifically, the dentifrice compositions according to the present invention significantly enhance the bioavailability of zinc.
2. Description of Related Art
Zinc compositions have been added to dentifrice compositions for controlling calculus. See for example, U.S. Pat. No. 4,100,269 to Pader.
PCT Application WO 96/03109 to Warner-Lambert Company teaches an antiseptic, anticaries dentifrice having a pH of about 3.0 to about 5.5. Acidifiers, including phosphoric acid, acidic phosphate salts, benzoic acid and food grade acids, such as citric acid, acidify the dentifrice. The dentifrice may also be buffered by salts of the acids such as citric acid-sodium citrate, phosphoric acid-sodium phosphate, sodium monobasic phosphate-sodium dibasic phosphate, acetic acid-sodium acetate, and benzoic acid and benzoate.
U.S. Pat. Nos. 4,545,979 and 4,550,018 to Ambike et al. teach a dental hygiene composition in an acidic pH range of from 3.0 to 5.0, pH buffers, fluoride, thymol, eucalyptol, methyl salicylate, peppermint and spearmint oil flavors, and 0.1 to 2.0 percent by weight of one or more highly pure alkali metal salts of dodecyl sulphate having less than 5% non-dodecyl alkyl sulphate salts.
Canadian Patent No. 834131 to Tisserand teaches a dentifrice preparation that has an acidic pH of about 3.8 to 5.8, optimally a pH of 4.0 to 5.5, and most preferably a pH of 4.0 to 4.8; fluoride; and contains flavor oils such as menthol, methyl salicylate or thyme oil and other flavors such that the composition is substantially free of hydrocarbon terpenes. According to Tisserand when essential oils which are not free of terpenes are employed in a fluoride dentifrice which has a pH in the range of about 3.8 to 5.8 the flavor develops a pronounced rancid and sour taste in a period of less than 3 months.
While the prior art discloses low pH toothpaste and other dentifrice compositions that contain zinc, there is a need for dentifrice compositions that deliver enhanced bioavailable zinc so that the effective zinc content can be lowered. It is believed that the zinc compounds tend to be astringent. Therefore, reducing the zinc content in the product can improve the consumer acceptability of the product.